Recently, needs for techniques of carrying out diagnosis or analysis inexpensively in a short time are greatly increasing in the fields of bedside diagnosis carrying out medical diagnosis near a patient, various DNA diagnoses, etc. Of these, an electrochemical measuring method is an extremely simple, inexpensive measuring method that can detect a measuring object if there are simply present electrodes serving to measurement, and a system for applying voltage and current. In addition, a method of electrochemically detecting and measuring a specified substance in a liquid specimen by a method of using a working electrode, a counter electrode and a reference electrode is well-known (e.g., see Patent Documents 1 and 2), and also it is widely known that this method is applied to detection and measurement of DNA (e.g., see Patent Documents 3 and 4).
In conventional electrodes used in electrochemical measurement, a general construction uses a rod-shaped electrode, for example, a gold electrode as a working electrode, for example, a silver-silver chloride electrode as a reference electrode, and for example, rod-shaped platinum as a counter electrode. FIG. 1 is an explanatory view for indicating the entire construction for a conventional electrochemical measurement method. Reference numeral 1 refers to a beaker (container for retaining an electrolytic solution), reference numeral 2 refers to an electrolytic solution, reference numeral 3 refers to a working electrode (e.g., a gold electrode), reference numeral 4 refers to a reference electrode (e.g., a silver-silver chloride electrode), and reference numeral 5 refers to a counter electrode (e.g., a platinum electrode). A commercially available beaker is used as the container for retaining the electrolytic solution, and as shown in FIG. 1, the various electrodes are maintained from above and placed in the electrolytic solution for electrochemical measurement.
The structure of the rod-shaped gold electrode as the working electrode uses for the tip end a material produced by molding, for example, rod-shaped gold with PEEK (polyether ether ketone) resin. This electrode can be repeatedly used by cleaning. Moreover, when the golf surface is deteriorated with flaws or the like, or in an experiment needed for uniformity of the gold surface such as immobilization of DNA, diamond for polishing and an alumina abrasive are used to polish the surface like a mirror finished surface on a glass plate for use.
In addition, in the case where the frequency in use is limited and there is relatively much time, for example, the electrode is experimentally used in a laboratory or the like, even such construction is sufficient in practical use. However, even in the use in such laboratory, when the frequency in use is high and there is little time in laboratory work, posing the problem of poor maintenance such as polishing. Moreover, considering the case where a measuring instrument using such electrode is used in the market as a product, there is a large obstacle for commercialization also from the viewpoints of cost performance, operability and maintenance.
A printed electrode is known that involves formation of three electrodes, i.e., a working electrode 7, counter electrode 8, and reference electrode 9 on the surface of a glass substrate 6 by a printing technique, for example, as shown in FIG. 2, as improvement measures for the above problems. However, such electrode is problematic in that the price is very expensive, the repeated reuse is limited, and the like. Moreover, an electrode configured to integrate analysis electrodes and an address electrode in a container (cuvette) for an electrolytic solution is proposed in Patent Document 5. However, this electrode also has a complex construction and might be extremely high in cost. In addition, although a complex sensor array for analyzing small amounts of multicomponents made by microfabrication and the like are proposed (Patent Document 6), the problems of electrode modules as described above are not solved yet.
Patent Document 1: Japanese Patent Laid-Open Publication No. 05-79989
Patent Document 2: Japanese Patent Laid-Open Publication No. 05-95223
Patent Document 3: Japanese Patent Laid-Open Publication No. 09-40372
Patent Document 4: Japanese Patent Laid-Open Publication No. 09-288080
Patent Document 5: Japanese Patent Laid-Open Publication No. 11-14584
Patent Document 6: Japanese Unexamined Patent Application Publication No. 2005-530179